1. Field of the Invention
The present invention relates to an uninterruptible duplexed power supply system for driving a load by the rectified output from a commercial alternating current power supply (AC), for instance, during normal operation and for driving the load by the output from a direct current power supply such as a rechargeable battery in the event of an abnormality such as a power outage, and more particularly relates to an uninterruptible duplexed power supply system used for the operation of critical devices such as burglar alarms, fire alarms, communications systems, information systems (such as server computers and factory automation personal computers), precision medical devices, and automated machinery, and to a unit plug-in structure for an uninterruptible duplexed power supply system. xe2x80x9cPower outagexe2x80x9d as used herein refers to the cutoff of the supply of power (current), such as when the power supplied from an electric company is cut off, or when the supplied power is cut off because a breaker is tripped, a device is unplugged, a wire is cut, or the like.
2. Description of the Related Art
Continuous, uninterrupted operation 24 hours a day for five years, for example, is required of server computers and the like in particular, and the power supply system shown in FIG. 9, for instance, is typical of the structure thereof. This system comprises an uninterruptible power supply (UPS) 90 connected to a commercial AC power supply, two switching power supplies 91 and 92 to which the switching power supply that serves as the server computer power supply is connected in parallel for the sake of safety (duplexing), and two sets of diodes 93 and 94 for preventing the current outputted from either of these switching power supplies 91 and 92 from sneaking into the other switching power supply, and is designed so that electrical power can be supplied at all times to the load. Therefore, if the switching power supply 91 should suffer a malfunction due to a lightning surge, any of various impulse surges, or the like being introduced into the AC input line, then the other switching power supply 92 will take over and be able to supply power to the load.
With the above structure, because the switching power supplies 91 and 92 are connected in series to the uninterruptible power supply 90, the total efficiency, which is obtained by multiplying the 75 to 80% efficiency of the switching power supplies 91 and 92 by the 75 to 80% efficiency of the uninterruptible power supply 90, is only about 55 to 64%, so there is a problem with energy loss.
Another problem is that because the uninterruptible power supply 90 and the two switching power supplies 91 and 92 are all separate components, not only is a large amount of space required, but the cost is also high.
Also, the two diodes 93 and 94 for preventing sneak current are required for each of the two switching power supplies 91 and 92, so a total of four or more diodes are required, which makes the system bulkier and leads to lower efficiency through diode forward loss.
The inventors have previously proposed a solution to the above problems. This is discussed in Japanese Patent No. 2,702,048, in which a primary circuit, equipped with a rectification circuit for rectifying the alternating current from a commercial AC power supply and switching elements or the like provided on the output side of this rectification circuit, is connected to the primary winding of a high-frequency transformer, a secondary DC output circuit that supplies power to the load is connected to the secondary winding of this high-frequency transformer, and a battery-side converter circuit equipped with switching elements or the like for operating according to the operating state of the primary circuit is connected to the tertiary winding of the high-frequency transformer. The result is an uninterruptible switching regulator (uninterruptible duplexed power supply system) that integrates the primary circuit (AC power supply circuit), the battery-side converter circuit, the switching circuit provided on the output side of these, and the secondary DC output circuit that supplies power to the load.
Nevertheless, although the load can be driven on an emergency basis by the battery-side converter circuit if the primary circuit should suffer a malfunction, the damaged parts in the malfunctioned primary circuit have to be replaced. This replacement requires that the computer be temporarily shut down by a specific operation, and the power supply then turned off, and this shutdown operation is not only troublesome, but the computer cannot be operated during the replacement work, resulting in the problem that the safety and reliability of the power supply cannot be fully ensured.
It is also difficult in structural terms to perform the above-mentioned replacement of damaged parts in the primary circuit right in the middle of (for a short time) the drive of the load by the battery-side converter circuit.
Accordingly, the method that had to be adopted up to now was to connect the above-mentioned uninterruptible switching regulator (uninterruptible duplexed power supply system) in parallel, just as with the switching power supplies 91 and 92 in FIG. 9. Furthermore because the connection is in parallel, the diodes 93 and 94 in FIG. 9 are needed to prevent sneak current, and the only effect is that the uninterruptible power supply (UPS) 90 is unnecessary, so there is still room for improvement in terms of reducing the size so as to take up less space, and lowering cost.
In light of the above situation, it is an object of the present invention to provide an uninterruptible duplexed power supply system that is highly reliable and has excellent durability, with which a more compact size and higher efficiency are both achieved, and with which a malfunction of the power supply circuit can be repaired in a live state.
In order to achieve the stated object, the present invention is characterized in. that there are provided a first unit that uses a first power supply as its input source and that houses a first primary circuit equipped with a switching element on the output side, and a second unit that uses the first power supply or a second power supply that is different from the first power supply and that houses a second primary circuit equipped with a switching element on the output side, a main component to which the outputs of the first unit and second unit are inputted comprises a primary winding of a high-frequency transformer to which the first unit and the second unit are connected via a connection component, a secondary DC output circuit that is connected to a secondary winding of the high-frequency transformer and supplies electrical power to a load, a PWM control circuit for keeping the output from this secondary DC output circuit at a constant voltage, and a battery-side converter circuit that is connected via a tertiary winding of the high-frequency transformer, is equipped with a switching element on the output side, and is used for charging a rechargeable battery for backup in the event of a power outage, the first unit and the second unit can be installed or removed in a live state between a connected state in which they are electrically connected to the two primary windings of the high-frequency transformer and a disconnected state in which this connected state has been released, and the output signals from the PWM control circuit are inputted to the gate circuits of the various switching elements of the first unit, second unit, and battery-side converter circuit.
Therefore, if the supply of power to the load is cut off due to a power outage in the input of the first unit and second unit, power can be instantaneously supplied from a rechargeable battery and the load can be driven on an emergency basis, without being shut down, for a time corresponding to the capacitance of the rechargeable battery. Also the durability of the power supply system can be enhanced compared to when only one unit is provided. Because two units are provided on the primary side so that two units are alternately driven, or when just one is driven during normal operation and the other is driven for emergency use, for example, and furthermore, even if one of the units should malfunction, the other unit can provide drive, allowing the load to be continuously driven even while the malfunctioning unit is being repaired. A commercial AC power supply may be used as the input for one of the two units, and the same commercial AC power supply as above, or a different power supply, such as a generator, a solar battery, or a rechargeable battery, may be used as the input for the other unit. If the voltage of the primary circuit drops below a specific voltage or drops to zero, then the switching element for the battery-side converter operating with the rechargeable battery as its input will switch from an idle or off state to an operating state and supply power from the rechargeable battery to the load as discussed above. The above-mentioned idle state refers to a state in which the switching element repeatedly turns on and off in synchronization with the switching element of the power supply circuit, but current does not flow.
After the unit containing the malfunctioned primary circuit has been removed, a unit containing a new (working) primary circuit is installed and the commercial AC power supply is once again turned on in a state in which the unit has been electrically connected to the primary winding of the high-frequency transformer. As a result, the switching element will switch to an idle or off state to halt the supply of power to the load by the battery-side converter circuit, and at the same time, the switching element of the connected unit automatically switches to an operating state, and the supply of power to the load by the battery-side converter circuit is switched to the supply of power by the unit, at, which point the switching of the power supply circuits is concluded.
When the input source of either the first unit or the second unit is a DC power supply, then the number of turns of the primary winding for connecting the first unit or second unit to the high-frequency transformer is changed to a number of turns corresponding to the DC voltage applied by the DC power supply.
Using a DC power supply for the input source as above allows the load to be driven by the DC power supply even if the commercial AC power supply should be cut off.
The first unit and the second unit can each be equipped with a load balancing terminal or a current balancing terminal, and the load balancing terminals or current balancing terminals of these units connected to each other, or a switching element drive pulse switching control circuit can be provided for switching the drive pulses for driving the switching elements of the first unit and second unit, and the drive of the two units controlled by this switching element drive pulse switching control circuit, thereby balancing the loads of the two units, or driving the two units at a preset balancing ratio, or driving the two units at a balancing ratio programmed into the computer that serves as the load.
If there are provided a malfunction detection circuit for detecting a malfunction of the first unit or second unit, a power outage detection circuit, an internal temperature detection circuit for detecting the internal temperatures of the two units, a cooling fan abnormal shutdown detection circuit for detecting the abnormal shutdown of a cooling fan, an input current detection circuit and current balancing detection circuit for the two units, and a charging control circuit for detecting the state of the rechargeable battery, such as the charge or discharge state of the rechargeable battery, the battery temperature, the remaining capacitance, or the estimated service life, and if maintenance is performed by transferring the detection signals from all of the above circuits by serial transfer to the computer that serves as the load, then the status of the uninterruptible duplexed power supply system can be ascertained and appropriate steps taken.
The present invention also provides a unit plug-in structure in an uninterruptible duplexed power supply system, wherein at least one of the first unit and second unit according to claim 1 is structured such that it can be plugged into a casing through an opening formed in the front thereof, the unit is provided with a connector capable of connecting to or separating from a connector provided to the casing side in the course of the plugging-in of the unit, and a plug-in operation member for pushing and moving the front of the unit when this unit is plugged in and for pulling and moving the unit when this unit is unplugged is attached to the casing so as to be swingable substantially around the horizontal axis.
Plugging the unit into the casing as above affords easy replacement and maintenance of the unit. Also, the swing force of the plug-in operation member is utilized as above so that the connectors whose numerous contacts have been fitted together when the unit was plugged in can be easily separated or connected. More specifically, when the unit is plugged in, the front of the unit is pushed and moved by the plug-in operation member, whereas when the unit is unplugged, the unit is pulled and moved by the plug-in operation member, which either connects or separates the connectors.
The plug-in operation member may be equipped with a latching component that latches with a latched component provided to the front of the unit when the plug-in operation member is swung in the plug-in direction of the unit and that unlatches when the plug-in operation member is swung in the unplugging direction of the unit, and fixing means may be provided for fixing the plug-in operation member to the casing in a state in which the unit has been completely plugged in.
This allows the plug-in operation member to be engaged with and disengaged from the unit merely by swinging the plug-in operation member as above. Also, fixing the plugin operation member to the casing by the fixing means in a state in which the unit has been completely plugged in effectively avoids the problem of the unit unintentionally coming unplugged.
The fixing means may comprise a latched component that is provided to the casing, a latching component provided to the plug-in operation member so as to be able to latch and unlatch the latched component, and a slot provided to a rotary shaft of the plug-in operation member so that the plug-in operation member will be able to move up and down when the unit has been completely plugged in.
With the above structure, the latching component of the plug-in operation member can be latched to or unlatched from the latched component on the casing side, and the unit fixed to or unfixed from the casing, merely by moving the plug-in operation member up or down in a state in which the unit has been completely plugged in.